Biological activities and chemical composition of lichens from Serbia

Abstract

The aim of this study is to investigate chemical composition of acetone extracts of the lichens Parmelia arseneana and Acarospora fuscata and in vitro antioxidant, antimicrobial, and anticancer activities of these extracts and gyrophoric acid isolated from A. fuscata. The HPLC-UV method was used for the identification of secondary metabolites. Stictic acid, norstictic acid, gyrophoric acid, usnic acid, atranorin and chloroatranorin were identified in the A. fuscata. In P. arseneana, we detected stictic acid, norstictic acid, usnic acid and atranorin, while gyrophoric acid was not identified. Antioxidant activity was evaluated by measuring the scavenging capacity of tested samples on DPPH and superoxide anion radicals, reducing the power of samples and determination of total phenolic compounds in extracts. As a result of the study, gyrophoric acid was found to have the largest DPPH radical scavenging activity with an IC50 value of 105.75 µg/ml. Moreover, the tested samples had an effective superoxide anion radical scavenging and reducing power. The total content of phenol in extracts was determined as pyrocatechol equivalent. The antimicrobial activity was estimated by determination of the minimal inhibitory concentration by the broth microdilution method. The most active was also gyrophoric acid, with minimum inhibitory concentration values ranging from 0.019 to 1.25 mg/ml. Anticancer activity was tested against LS174 (human colon carcinoma cell line), A549 (human lung carcinoma cell line), Fem-x (malignant melanoma cell line), and a chronic myelogeneous leukaemia K562 cell line using the MTT method. Extract of P. arseneana expressed the strongest anticancer activity against all cell lines with IC50 values ranging from 11.61 to 47.06 µg/ml.

Keywords: HPLC analysis; biological activities; lichens; lichens compound.

Table 1. Retention time of the examined lichen substances and their absorbance maxima (nm)

Table 2. DPPH radical scavenging activity and superoxide anion scavenging activity of acetone extracts of Parmelia arseneana and Acarospora fuscata and isolated gyrophoric acid

Table 3. Reducing power of acetone extracts of Parmelia arseneana and Acarospora fuscata and isolated gyrophoric acid

Table 4. Total phenolics content of acetone extracts of Parmelia arseneana and Acarospora fuscata

Table 5. Minimum inhibitory concentration (MIC) of acetone extracts of Parmelia arseneana and

Acarospora fuscata and isolated gyrophoric acid

Table 6. Growth inhibitory effects of acetone extracts of Parmelia arseneana and Acarospora fuscata and isolated gyrophoric acid on FemX, A549, LS174 and K562 cell lines

Figure 1. Chromatogram of the standards used for the identification of compounds present in Acarospora fuscata and Parmelia arseneana

Figure 2. The HPLC chromatogram acquired at 254 nm of the extracts from Acarospora fuscata and Parmelia arseneana

Figure 3. UV spectrum of gyrophoric acid

Figure 4. Cell-cycle distribution after 24 h of continuous action of (IC₅₀) P. arseneana, A. fuscata and Gyrophoric acid in FemX and K562 cell lines. Representative histograms of cell-cycle distribution of malignant cells measured by flow cytometric analysis of DNA content after treatment